FAQ

Strength of metals is normally measured by the tensile strength as the main measure although this is not the only property as hardness is another big factor. Basically, iron is soft and steel is hard. Plain iron is stretchy and does not corrode quickly, whereas steel is much stiffer and corrodes more quickly. The tensile strength of cold worked iron is about half that of an average steel, likewise the hardness is about half that of steel too. Pure iron, which is rarely used, is even weaker and softer again and a bit more like softer materials like copper and aluminium. Where confusion comes in is that there is another iron - Cast Iron - which is totally different to both iron and steel. Cast iron is very hard and tough but incredibly brittle so its properties are very different.s

Steel doesn't anodize in the sense that aluminum and some other metals do. However, it can be heat-colored. The trick is to clean the surface first (it must be oxide free), then heat gently until the colors appear. These are called temper colors in steel. They are due to a thin adherent layer of oxide that forms and thickens as temperature is increased. They are quite temperature dependent. As the steel is heated, the first color to appear is pale yellow. This will progress through darker yellows, browns, purples, and blues as the temperature rises. Above blue, the oxide becomes the gray/black color you are apparently getting - this is the result of heating too fast and too hot. See the chart at the site below for colors in plain carbon steel. Note that the temperatures are pretty low - It all starts around 400 F and if you go above 600 F the show's all over.s

Foam steel [often steel foam] is used in applications that require light weight but high rigidity and strength. Watertight doors on modern ships are often made of foam steel. Pressure doors on aircraft are possible uses. As we keep striving for lighter weights in cars, foam steel might have some useful applications in bodies. There is a technical paper online that is in .pdf format that has a good discussion of the process and characteristics of foam steel.s

There are lightweight steel alloys that are lighter, for a given volume, than pig iron. The words iron and steel have referred to different materials at different times, and are used in different ways. A steel structure may also be lighter because steel alloys are stronger, in a given cross-section, that iron or other types of steel. For example, a 1-inch bar of chrome-vanadium steel is stronger than a 1-inch bar of 4130 mild steel or pig iron. The more you find out about it, the more complicated it is. But the answer to your question is (a) Yes, and (b) it's all relative.s

Extruded steel is only the steel being run through a die when it is heated, it usually reduces the size of the grain of the steel itself, enhancing toughness. Realistically though, in a handgun, it doesn't matter if the frame is cast or forged, both types will hold up to any amount of abuse, unless you use it as a sledgehammer, and are splitting stones with it, then the forged frame would win. 4140 is more than adequate for a slide/frame. Hell, even mild steel would be adequate as long as you don't mind some dings and scratches, and again, don't use it as a sledgehammer...s